Gaseous nitrous acid analyzer with field calibration function

Abstract

The utility model relates to a gas monitoring technology, and particularly provides a gaseous nitrous acid analyzer with a field calibration function, which comprises a sampling unit, a separation unit and an analysis unit which are connected in sequence, the gas-state nitrous acid analyzer also comprises a standard gas generation unit; the standard gas generation unit comprises a spiral heat conduction pipe which is cast in a base body by a heat conduction medium; the TEC is fixed on the base body, and the temperature sensor is arranged in the base body. The device has the advantages of low energy consumption and the like.

Description

Technical Field

[0001] This utility model relates to gas monitoring technology, and in particular to a gaseous nitrous acid analyzer with on-site calibration function. Background Technology

[0002] The ambient air gaseous nitrous acid analyzer is an analytical instrument used for automatic monitoring of gaseous nitrous acid (HONO) in ambient air. The sampling absorption unit uses HONO absorbent to absorb HONO in the air. The absorbent containing HONO in the air is then transported to the analysis unit for detection through a gas-liquid separation device. The separated gas is then discharged into the air through a downstream gas mass flow meter (MFC) and a sampling pump.

[0003] Currently, most HONO monitoring methods employ wet chemical methods. Since commercially available gaseous nitrite standard gas is unavailable, calibration is primarily performed using standard solutions or by using self-made standard gas generators.

[0004] The above-mentioned gaseous nitrous acid analyzer has some problems, such as:

[0005] 1. The standard solution calibration method has gas-liquid conversion error and cannot directly and accurately characterize the gas measurement accuracy.

[0006] The method of generating standard gas using a self-made standard gas generator involves mixing non-volatile H2SO4 with nitrite solution in a bubbling reactor to produce HONO standard gas. An existing improved method uses a glass spiral tube reactor as the HONO generating unit, achieving HONO gas preparation through water bath temperature control of the glass spiral tube. This water bath method requires an external water bath, using a peristaltic pump and tubing to introduce water from the water bath into the generating unit and then out, repeating this cycle. During water transfer, temperature control accuracy decreases, and the water bath cannot maintain temperature control accuracy during dynamic water flow. Furthermore, the water bath method places high demands on instrument installation, typically requiring a line-contact installation.

[0007] 2. Because HONO absorbent contains a large amount of hydrochloric acid, which is volatile, even if a gas-liquid separation device is used to separate the gas from the hydrochloric acid absorbent, acid mist will still enter the MFC and sampling pump at the end of the gas path. In addition, HONO absorbent contains sulfonamide and nylondiamine hydrochloride. The sampling pump has a large suction force, which can easily draw a small amount of HONO absorbent into the MFC at the end in the form of droplets, forming crystals. Both hydrochloric acid mist and crystals will cause corrosion of the MFC and sampling pump, leading to damage. Utility Model Content

[0008] To address the shortcomings of the existing technical solutions, this utility model provides a gaseous nitrous acid analyzer with on-site calibration function.

[0009] The objective of this utility model is achieved through the following technical solution:

[0010] A gaseous nitrous acid analyzer with on-site calibration function includes a sampling unit, a separation unit, and an analysis unit connected in sequence; the gaseous nitrous acid analyzer also includes a standard gas generating unit, which comprises:

[0011] A spiral heat pipe, wherein the spiral heat pipe is cast into a base by a heat-conducting medium;

[0012] A TEC and a temperature sensor are provided, wherein the TEC is fixed on the substrate and the temperature sensor is disposed within the substrate.

[0013] To prevent hydrochloric acid mist and absorbent droplets in the gas (output from the separation unit) from damaging downstream devices, the analyzer further includes an absorption unit connected to the gas outlet of the separation unit. The absorption unit includes:

[0014] The tank body has openings at both ends, and the end caps are inserted into both ends respectively. Each end cap has a gas passage.

[0015] A sealing ring, which surrounds the outer radial side of the tank body and is disposed between the tank body and the end cap;

[0016] A packing bag and anhydrous sodium carbonate, wherein the packing bag is disposed inside the tank and the anhydrous sodium carbonate is filled in the packing bag;

[0017] A sealing gasket is disposed axially in the tank body and is compressed by the end cap and the end of the tank body.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] 1. This application uses a metal tube as a reactor, increases the chemical reaction contact area in a spiral tube manner, and forms a casting matrix by aluminum casting. The good temperature conductivity of aluminum and the casting mode enable the internally embedded metal tube to achieve the maximum temperature contact area and achieve uniform temperature control, thereby improving the temperature uniformity and stability of the generation unit, thus improving the generation efficiency and generation stability of HONO standard gas, serving the on-site calibration of the analyzer, and realizing the on-site calibration function;

[0020] The bottom surface of the cast substrate is designed with TEC mounting slots for installing TEC, directly turning the cast substrate into a cold core, improving refrigeration efficiency and reducing energy consumption;

[0021] 2. Optimize the sealing method between the heat sink, TEC, and cast substrate, and design additional O-ring mounting grooves in different areas to prevent condensation from damaging the TEC and reduce the TEC failure rate;

[0022] 3. A temperature sensor area is designed in the center of the casting substrate. Due to the good thermal conductivity of aluminum, placing the temperature sensor in this position can reflect the actual temperature of the stainless steel tube to the greatest extent. Copper foil is wrapped around the temperature sensor instead of the conventional thermal grease to fill the installation holes in the casting substrate. No additional thermal grease needs to be added later, reducing the workload of operation and maintenance.

[0023] 4. Compared with the water bath temperature control method using glass components, the cast-based generating unit has no risk of component damage or leakage, high reliability, no consumables, and requires no maintenance.

[0024] 5. The absorption unit replaces the conventional sodium hydroxide absorption method, thereby effectively removing hydrochloric acid mist and absorbent droplets, improving the removal efficiency of hydrochloric acid mist while avoiding the introduction of other corrosive liquids or chemical reagents;

[0025] 6. The absorption unit adopts radial and axial sealing, which has good airtightness and low requirements for the consistency of tank processing. This design can meet the needs of tanks of different materials, with low processing cost, high yield, and easy installation and disassembly.

[0026] 7. Using PTFE material with a pore size of 0.2μm as the packing bag, anhydrous sodium carbonate is filled into the packing bag, which can not only prevent the tank lid from being unable to be opened after the anhydrous sodium carbonate absorbs and clumps, but also filter the anhydrous sodium carbonate particles.

[0027] 8. The sealing gasket is pressed tightly against the filter membrane to ensure that the sealing gasket can be reused when the tank is disassembled and the packing is replaced;

[0028] 9. Anhydrous sodium carbonate and PTFE filter membranes are used as consumables, which are easy to replace, reduce the difficulty of maintenance and disassembly, protect back-end components, and extend the life of the instrument. Attached Figure Description

[0029] The disclosure of this utility model will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this utility model and are not intended to limit the scope of protection of this utility model. In the drawings:

[0030] Figure 1 This is a perspective structural diagram of the standard gas generating unit according to Embodiment 1 of this utility model;

[0031] Figure 2 This is a partial structural diagram of the standard gas generating unit in Embodiment 1 of this utility model;

[0032] Figure 3 This is a schematic diagram of the absorption unit according to Embodiment 1 of this utility model.

[0033] In the attached diagram, 11-tank body, 21-first end cap, 22-second end cap, 31-sealing ring, 32-sealing gasket, 41-compression nut, 42-filter membrane, 43-nonwoven fabric, 51-heat pipe, 61-substrate, 71-TEC, 81-temperature sensor, 91-radiator, 92-screw, 93-heat insulation pad, 94-outer casing, 611-annular part. Detailed Implementation

[0034] Figures 1-3 The following description illustrates optional embodiments of the present invention to teach those skilled in the art how to implement and reproduce it. For the purpose of teaching the technical solutions of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the present invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present invention. Therefore, the present invention is not limited to the following optional embodiments, but is defined only by the claims and their equivalents.

[0035] Example 1

[0036] This embodiment provides a gaseous nitrous acid analyzer with on-site calibration function, comprising a sampling unit, a separation unit, and an analysis unit connected in sequence, all of which are existing technologies in the field.

[0037] like Figure 1 As shown, the (gaseous nitrous acid) standard gas generating unit includes:

[0038] The spiral heat pipe 51 is cast into the substrate 61 by a heat-conducting medium.

[0039] TEC71 is fixed on the substrate 61 and is used to adjust the temperature of the substrate 61, that is, to adjust the temperature of the heat pipe 51. Temperature sensor 81 is set inside the substrate 61 to obtain the temperature of the heat pipe 51 in real time.

[0040] To prevent condensation from damaging the TEC71, further, such as Figure 2 As shown, the generating unit further includes:

[0041] The heat sink 91 is connected to the TEC71. The heat sink 91 is fixed to the base 61 using screws 92.

[0042] The heat insulation pad 93 surrounds the substrate 61 and is located between the radiator 91 and the outer casing 94.

[0043] The sealing ring 31 is disposed axially between the radiator 91 and the heat insulation pad 93, between the base 61 and the heat insulation pad 93, and between the heat insulation pad 93 and the outer casing 94.

[0044] To obtain accurate temperature, the temperature sensor 81 is further wrapped with copper foil and disposed within a blind hole in the substrate 61.

[0045] To prevent hydrochloric acid mist and absorbent droplets in the gas (output from the separation unit) from damaging downstream devices, the analyzer also includes an absorption unit connected to the gas outlet of the separation unit, such as... Figure 3 As shown, the absorption unit includes:

[0046] The tank body 11 has openings at both ends, and the first end cap 21 and the second end cap 22 are inserted into the two ends respectively. The first end cap 21 and the second end cap 22 each have a gas passage.

[0047] The sealing ring 31 surrounds the outer radial side of the tank body 11 and is disposed between the tank body 11 and the first end cap 21, and between the tank body 11 and the second end cap 22, thereby achieving a radial seal.

[0048] A packing bag is placed inside the tank 11, and anhydrous sodium carbonate is filled in the packing bag to remove hydrochloric acid from the gas.

[0049] The sealing gasket 32 ​​is positioned axially on the tank body 11 and is squeezed by the first end cap 21 and one end of the tank body 11, as well as by the second end cap 22 and the other end of the tank body 11, thereby achieving axial sealing.

[0050] To further achieve better axial sealing, the absorption unit also includes:

[0051] A clamping nut 41 is disposed between the first end cap 21 and the sealing gasket 32, and between the second end cap 22 and the sealing gasket 32. The first end cap 21 and the second end cap 22 respectively have grooves for accommodating the clamping nut 41.

[0052] To further prevent the packing packing from being blocked, the absorption unit also includes:

[0053] The filter membrane 42 is disposed between the clamping nut 41 and the sealing gasket 32 ​​to block the packing pack.

[0054] Example 2

[0055] Application example of the gaseous nitrous acid analyzer with on-site calibration function according to Embodiment 1 of this utility model.

[0056] In this application example, the analyzer includes a sampling unit, a separation unit, and an analysis unit connected in sequence. The separation unit uses a gas-liquid separator. The gas outlet is connected in sequence to the absorption unit, the mass flow meter, and the sampling pump, while the liquid outlet is connected to the analysis unit.

[0057] like Figure 1As shown, the stainless steel spiral heat pipe 51 has an inner diameter of 2mm and a length of 4m, and is cast in aluminum within a cylindrical substrate 61. The two ends of the heat pipe 51 are located on the outside of the substrate 61.

[0058] The temperature sensor 81 is wrapped with copper foil and placed inside the central blind hole of the substrate 61.

[0059] like Figure 2 As shown, TEC71 is fixed in the groove at the end of the substrate 61 to adjust the temperature of the substrate 61, which in turn adjusts the temperature of the heat pipe 51.

[0060] The end of the base 61 has an annular portion 611 extending radially outward. A heat sink 91 with heat dissipation teeth is fixed to the annular portion 611 by screws 92, and the TEC71 is sandwiched between the heat sink 91 and the base 61.

[0061] The heat insulation pad 93 surrounds the substrate 61, located on the radially outer side and axial side of the annular portion 611, and has an L-shaped cross-section. The heat insulation pad 93 is sandwiched between the radiator 91 and the outer casing 94.

[0062] The sealing ring 31 is disposed axially between the radiator 91 and the heat insulation pad 93, between the base 61 and the heat insulation pad 93, and between the heat insulation pad 93 and the outer casing 94.

[0063] like Figure 3 As shown, the first end cap 21 has a gas flow channel extending along its central axis. The second end cap 22 has a gas flow channel extending along its central axis and a gas passage extending in a direction perpendicular to the central axis. A circular groove is provided axially in the second end cap 22, and non-woven fabric 43 and a clamping nut 41 are disposed in the groove. A PTFE filter membrane 42 and a PTFE sealing gasket 32 ​​are disposed between the end face of the second end cap 22 and the end face of the tank body 11. The PTFE filter membrane 42 and the PTFE sealing gasket 32 ​​(with a thickness of 0.4 mm) are pressed between the second end cap 22 and the tank body 11 to achieve an axial seal. Similarly, the first end cap 21 and the tank body 11 adopt the same structure.

[0064] The inner walls of the second end cap 22 and the first end cap 21 each have annular grooves. A fluororubber sealing ring 31 is disposed in the annular groove and is squeezed between the second end cap 22 and the radial outer side of the tank body 11. The radial compression of the sealing ring 31 is 10%-15%, thereby achieving radial sealing.

[0065] Anhydrous sodium carbonate is filled into a PTFE packing bag with a pore size of 0.2μm. The packing bag is placed inside the tank 11 to remove hydrochloric acid from the gas.

[0066] During operation, the reaction liquid enters the heat pipe 51. Using a combination of TEC71 and temperature sensor 81, the temperature of the substrate 61 is maintained at the set temperature. The reaction liquid generates gaseous nitrous acid in the spiral heat pipe 51, thus providing nitrous acid on-site and enabling on-site calibration. The specific calibration method is existing technology in this field.

[0067] Meanwhile, the absorption unit effectively absorbs hydrochloric acid mist and small droplets of HONO absorbent in the gas, protecting the downstream gas mass flow meter and sampling pump from corrosion by hydrochloric acid mist, and preventing crystallization due to the adhesion of HONO absorbent. The anhydrous sodium carbonate packing and filter membrane 42 in the absorption unit are replaced every 3 months.

[0068] The HONO standard gas generation efficiency of the standard gas generation unit in this application has been increased from 55% to 95%, and the repeatability has been increased from 10% to 2%. After more than one year of field use, the failure rate is 0%.

[0069] The instrument equipped with the updated absorption unit has been in field use for over two years. In contrast, existing instruments without this absorption unit require replacement of the MFC and sampling pump every six months on average. Therefore, the application of this absorption unit not only effectively extends the lifespan of the devices but also significantly reduces instrument maintenance costs.

Claims

1. A gaseous nitrous acid analyzer with on-site calibration function, comprising a sampling unit, a separation unit, and an analysis unit connected in sequence; characterized in that, The gaseous nitrous acid analyzer further includes a standard gas generating unit, which comprises: A spiral heat pipe, wherein the spiral heat pipe is cast into a base by a heat-conducting medium; A TEC and a temperature sensor are provided, wherein the TEC is fixed on the substrate and the temperature sensor is disposed within the substrate.

2. The gaseous nitrous acid analyzer according to claim 1, characterized in that, The generating unit further includes: A radiator connected to the base, wherein the TEC is sandwiched between the radiator and the base; A heat insulation pad, the heat insulation pad surrounding the base and disposed between the radiator and the outer casing, the outer casing surrounding the base; The sealing rings are respectively disposed between the radiator and the heat insulation pad, between the substrate and the heat insulation pad, and between the heat insulation pad and the outer casing.

3. The gaseous nitrous acid analyzer according to claim 1, characterized in that, The temperature sensor is wrapped with copper foil on the outside and placed inside a blind hole in the substrate.

4. The gaseous nitrous acid analyzer according to claim 1, characterized in that, The end of the substrate has a groove to accommodate the TEC.

5. The gaseous nitrous acid analyzer according to claim 1, characterized in that, The analyzer further includes an absorption unit connected to the gas outlet of the separation unit, the absorption unit comprising: The tank body has openings at both ends, and the end caps are inserted into both ends respectively. Each end cap has a gas passage. A sealing ring, which surrounds the outer radial side of the tank body and is disposed between the tank body and the end cap; A packing bag and anhydrous sodium carbonate, wherein the packing bag is disposed inside the tank and the anhydrous sodium carbonate is filled in the packing bag; A sealing gasket is disposed axially in the tank body and is compressed by the end cap and the end of the tank body.

6. The gaseous nitrous acid analyzer according to claim 5, characterized in that, The absorption unit further includes: A filter membrane is disposed between the end cap and the sealing gasket to block the packing package.

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